This invention relates to the field of lawn maintenance and particularly to sprinklers of the pop-up type which are permanently installed in the lawn and supplied with water at will or on schedule by remote valve operation. Such sprinklers are known, but in the past have suffered from certain imperfections. Permanently installed equipment should operate without failure for long intervals, but it has been found common for unwanted material to find its way into the path of the moving members of such sprinklers, particularly during their retraction. In an effort to overcome this, it has been proposed, in Hayes et al. U.S. Pat. No. 3,921,910, for example, to provide a wiping seal which engages the moving member and removes particles as they reach the seal. It will be realized that under conditions where considerable unwanted material may accumulate, the patented structure may amass so much material as to render itself inoperative.
It is also desirable to prevent water borne material from reaching the spray heads and clogging them. Strainers are common in water lines, but are not always effective for desirable intervals, and are frequently difficult or inconvenient to remove for cleaning or replacement.